(The
Totten Glacier of East Antarctica contains about as much ice mass as
all of West Antarctica. Its catchment basin is roughly the size of
the U.S. Southeast. Much of it sits below sea level. And an ice shelf
buttressing the glacier’s largest outlet in a 6 mile wide and 3,600
foot deep canyon is rapidly melting. Once this ice shelf breaks
apart, ocean water will flood inland along a reverse slope and the
Totten Glacier will increase its rate of movement toward the ocean —
significantly speeding rates of global sea level rise. Image
source: Australian
Antarctic Division.)

…several
lines of evidence support the conclusion that rapid basal melt of the
[Totten Ice Shelf] is driven by the flux of warm [modified
circumpolar deep water] into the cavity: the presence of warm water
at the ice front, the existence of a deep trough providing access of
this warm water to the cavity, direct measurements of mass and heat
transport into the cavity, the signature of glacial meltwater in the
outflow, and exchange rates inferred from the heat budget and
satellite-derived basal melt rates.

Presently,
because the ice shelf floats, this melt is not adding to global sea
level rise. But the shelf acts like a cork that’s stopping the rest
of Totten from flowing into the ocean. And when the ice shelf weakens
enough, it will rift and break apart — leaving the massive glaciers
behind it exposed to the inrush of warm waters and removing the last
major barrier preventing them from bursting out.